1. Field of the Invention
The present invention generally relates to a UV sterilization system. Specifically, the present invention is directed toward a UV sterilization system utilized within a linear form, fill and seal packaging machine.
2. Description of the Related Art
The sterilization of packaging containers such as gable-top cartons, has been accomplished through irradiation with ultraviolet ("UV") energy. In such a sterilization system, an UV lamp is mounted above the conveyor line of a packaging machine. The UV lamp irradiates the container as the container passes below the UV lamp, usually just prior to filling of the container with a flowable food product such as milk.
In order to have an effective kill of microorganisms, the UV energy must meet a minimum level of watts/cm.sup.2 -sec. The disinfection of the cartons depends on the combination of intensity of UV radiation and exposure time (dose). If during the conveyance of containers under the UV lamp, the intensity of the UV lamp is below the minimum level, then the containers may not receive a sufficient amount of UV energy and may not be properly sterilized. The operator would have no knowledge of such non-sterilization, thus possibly resulting in the distribution of a contaminated container to the public. More likely, the operator would eventually notice the lack of intensity, and the entire batch would have to be discarded since the operator would be unable to detect exactly when the intensity decreased below the minimum level. Such a scenario would prove economically painful to a dairy, or other food packager.
Another operational problem associated with UV sterilization systems is starting the UV lamp in a cold environment. In a mercury UV lamp, it is the heating and vaporization of the mercury which creates the UV radiation. Contained within the shell of the UV lamp is the mercury and an inert gas. An anode is at one end of the UV lamp and a cathode is at the other end of the UV lamp. When a sufficient voltage is delivered to the UV lamp, an arc is struck across the UV lamp. If the temperature is too cold, under 8.degree. C., then the voltage from a power supply may be insufficient to strike an arc across the UV lamp. Also, it is often the case that the UV lamp must be shut down during a product run to provide repair or correct a problem on the line. The problem does not need to be associated with the UV lamp to necessitate its inactivation. When such a shut down occurs, the downtime is further amplified by the added start-up time for the UV lamp. The reason for the increased downtime arises from the necessity of having to wait for the vaporized mercury to cool down and have sufficient condensation to again create an arc across the UV lamp. Too much mercury in the vapor phase within the UV lamp shell will interfere with the striking of an arc between the anode and cathode via the inert gas, thus, an operator must wait for the mercury to condense in order to strike an arc in the UV lamp, and restart the UV lamp.
Resolution of these problems would further enhance the efficiencies of dairies, juice packagers, and other flowable food packagers who utilize form, fill and seal packaging machines having sterilization features, and in particular those facilities in cold environments.